Epigraphs.

Yesterday evening as I sat happily ensconced in a cinema showing of The Hobbit, a line spoken by Gandalf jumped out at me, waking me from the beauty-induced-stupor of Rivendell. And it got me to thinking of epigraphs.
So often, I ignore them as they sit quietly nestled in the unread front pages of a work. And yet, perhaps if I had read them, the events which followed would seem more lucid, more clear, more meaningful.
Anyway, this quote struck me to the core. It seemed to add a level of meaning to my own work when applied to it, and it made me appreciate once more the power of a relevant epigraph.
What are your thoughts on the use of epigraphs? Have you ever used them in your own work?